It is known that numerous pieces of furniture are mounted on castors so as to make them easy to move. Nevertheless, with a seat, and in particular an armchair, it is often required that the seat can be moved easily while a person is sitting on it, but that in contrast it should be more difficult to move when unoccupied.
To do this, castors for mounting on seats can be provided with a brake system which is not engaged so long as a person sitting on the chair, and which is engaged when the chair is empty.
Such castors have already been made, such as those described in EP-A-0 645 262 and EP-A-1 110 757. In general, a castor of that type comprises a body; means for connecting said body to furniture, e.g. a pivot; a rotary bearing wall defined substantially in a first plane; means for securing the bearing wall to the body; at least one wheel, and advantageously two wheels, each including a respective first orifice defined on a first axis; a rotary shaft of section complementary to the orifice, and defining a second axis; and means for mounting said rotary shaft in co-operation with said first bearing wall, the rotary shaft also being suitable for being engaged in said orifice in such a manner that the first and second axes coincide to enable the wheel to pivot about the second axis.
The castors for furniture or the like that are presently known on the market, such as those described and shown in the two above-referenced documents, give satisfaction in terms of operation, but they present the following drawback: the complexity of their structure involves a relatively large number of component parts being provided, with said parts being awkward to assemble together.